Made changes to support the quantikz package

[ArvinSKushwaha]

To resolve issue #2842, I have followed the format of the commits for issue #2755 to both correctly classify the quantikz environment (for the quantikz package) and test the changes.

[lervag]

Your code didn't work immediately because you forgot to give the function a name. Notice my diff that fixed it:

diff --git a/autoload/vimtex/syntax/p/quantikz.vim b/autoload/vimtex/syntax/p/quantikz.vim
index 82f9369a..5599a3c8 100644
--- a/autoload/vimtex/syntax/p/quantikz.vim
+++ b/autoload/vimtex/syntax/p/quantikz.vim
@@ -4,7 +4,7 @@
 " Email:      karl.yngve@gmail.com
 "
 
-function! vimtex#syntax#p#quantikz(cfg) abort " {{{1
+function! vimtex#syntax#p#quantikz#load(cfg) abort " {{{1
   call vimtex#syntax#core#new_env({
         \ 'name': 'quantikz',
         \ 'starred': v:false,

[ArvinSKushwaha]

Ah, thank you!

[lervag]

No problem :)